Is there a difference in mean time weighted Disease Activity Score in 28 joints (DAS28-ESR) after optimizing the serum trough concentrations > 15 mg/L in RA patients who are randomly assigned to continuation of the standard dose or to prolong the dose interval from weekly to every 2 weeks.
We Hypothesis that there would be no difference in in mean time weighted DAS28-ESR after optimizing the serum trough concentrations > 15 mg/L in RA patients between the two study arms.
28 week open label, non-inferior, multicenter, randomized controlled study.
This study will include consecutive RA patients with a tocilizumab concentration above 15 mg/L who have been treated with subcutaneous tocilizumab weekly for at least 6 months.
The tocilizumab dose-interval will be prolonged in patients with tocilizumab concentration above 15 mg/L from 162 mg weekly to 162 mg every 2 weeks.
The difference in mean time weighted DAS28 /SDAI/CDAI of RA patients with serum tocilizumab > 15 mg/L who are randomly assigned to continuation of the standard dose or to increase dosing interval to every 2 weeks.
The number of flares after 28 weeks
The change in drug levels after 28 weeks of intervention compared to baseline
Change in Patient Reported Outcome Measurements, measured in mean time weighted Routine Assessment of Patient Index Data (RAPID) score.
Patients perceptive towards optimising doses with therapeutic drug monitoring after 28 weeks
SAMPLE SIZE/DATA ANALYSIS
A total sample size of 98 patients is needed. Given an anticipated dropout rate of 10% and that 37% of the patients will have drug levels < 15 mg/L, 31 patients will be included per group.
Mixed model analyses will be used to analyse the primary endpoint (DAS28 over time). Secondary endpoints with be analysed with t-tests, Mann-Whitney tests, and chi-square tests as appropriate.